Wadley made a pair of baskets that put LSH up 55-49, but Steidler's 3-pointer off an inbound play tied the game again at 56 with three intense minutes to play.
"We knew this was going to be a game of runs," first-year coach Sean Keating said. "You try to take away their transition, but you just have to have poise and patience. These kids have been in games like this before, and that experience paid off."
A pair of free throws by Jordan Kahlow put the Giants up two, but reserve Nick Rosburg, who had 12 of his 14 points in the second half, made a free throw to cut the lead to one. Rosburg had two more free throws that could have won with 6 seconds to play, but he missed, and Bartlett grabbed the rebound, getting fouled.
He made two free throws for the lead, and the Giants weren't able to get a good look in the last three seconds. Bartlett scored all 10 of his points in the second half.
"I was very confident," Keating said. "He's a warrior, he's battled through two ACL surgeries. He's the guy you want at the line."
Brendan Reese and Steidler each scored 11 points, and Steidler had seven rebounds, one more than Bartlett, who was a reserve on St. Peter's state-tournament team in 2012.
Kahlow led LSH (16-12) with 14 points, with Riley McGraw scoring 11 and Wadley with 10. Brady Rose had nine points and 11 rebounds.
St. Peter (14-14) will play in the Class AA quarterfinals Wednesday at 6 or 8 p.m, at either Williams Arena or Target Center. The pairings will be determined today.
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